Dislocation nucleation mechanisms during nanoindentation of concentrated FeNiCr alloys: unveiling the effects of Cr through molecular simulations

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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Modelling and Simulation in Materials Science and Engineering, Volume 30, issue 8
Fe-based alloys with high chromium and nickel concentrations are very attractive for efficient energy production in extreme operating conditions. We perform molecular dynamics (MD) simulations of nanoindentation on fcc FeNiCr multicomponent materials. Equiatomic FeNi, Fe55Ni19Cr26, and Fe74Ni8Cr18 are tested by using established interatomic potentials and similar conditions, for the elucidation of key dislocation nucleation mechanisms and interactions. Generally, we find that the presence of Cr in these alloys reduces the mobility of prismatic dislocation loops, and increases their area, regardless of crystallographic orientation. Dislocation nucleation and evolution is tracked during mechanical testing as a function of nanoindentation strain and Kocks-Mecking continuum modeling displays good agreement with MD findings. Furthermore, the analysis of geometrically necessary dislocations (GNDs) is consistent with the Ma-Clarke’s model at depths lower than 1.5 nm. The presence of Cr leads to a decrease of the GNDdensity with respect to Cr-less FeNi samples, thus we find that Cr is critically responsible of increasing these alloys’ hardness. Post-indentation impression maps indicate that Ni-Fe-Cr compositions display strain localization and hardening due to high Cr concentration.
Funding Information: We would like to thank Professor Lukasz Kurpaska for fruitful experimental discussions related to nanoindentation tests. We acknowledge support from the European Union Horizon 2020 research and innovation program under Grant Agreement No. 857470 and from the European Regional Development Fund via the Foundation for Polish Science International Research Agenda PLUS program Grant No. MAB PLUS/2018/8 (R A D, S P, and M J A). This work has been partially supported by the National Science Centre through the Grant No. UMO-2020/38/E/ST8/00453 (F J D G and A U). We acknowledge the computational resources provided by the High Performance Cluster at the National Centre for Nuclear Research in Poland, as well as the support of the Interdisciplinary Centre for Mathematical and Computational Modelling (ICM) University of Warsaw under computational allocation No. g88-1181. Publisher Copyright: © 2022 The Author(s). Published by IOP Publishing Ltd.
continuum model, dislocation dynamics, MD simulations, nanoindentation, Ni alloys, Plasticity
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Dominguez-Gutierrez , F J , Ustrzycka , A , Xu , Q Q , Alvarez-Donado , R , Papanikolaou , S & Alava , M J 2022 , ' Dislocation nucleation mechanisms during nanoindentation of concentrated FeNiCr alloys: unveiling the effects of Cr through molecular simulations ' , Modelling and Simulation in Materials Science and Engineering , vol. 30 , no. 8 , 085010 . https://doi.org/10.1088/1361-651X/ac9d54